Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

After falling 135 points yesterday, the Dow Jones Industrial Average (^DJI 0.15%) is up 20 points as of 1 p.m. EST. But the index had been up by 72 points earlier this morning. The S&P 500 and the Nasdaq were also both higher this morning before falling into the red; the S&P 500 is off by 0.03% and the Nasdaq is down 0.31%.

A few individual stocks have followed the same up-then-down path today.

After trading 4% higher this morning, shares of Sirius XM (SIRI 4.53%) are now only up 1.1%. The jump this morning came after analyst at Evercore upgraded the stock from equal weight to overweight and increased its price target from $3.90 to $4.50. My colleague Rick Munarriz believes the rating change comes at the right time, as shares of Sirius XM have been stumbling for four weeks and the valuation has come down slightly during that time. Furthermore, the monthly satellite radio subscription was increased at the start of the year from $14.49 to $14.99. That increase should help the company with its profitability as long as subscribers don't leave based on this bump.  

Hertz (HTZG.Q) also saw a big pop earlier in the day only to come back down to earth. Around 11 a.m. EST shares of the rental car company were up more than 3.9%, hitting $29.81, which happens to be the company's highest intraday price since it went public in November 2006. Shares are now only trading higher by 0.84%. The big jump came after CNBC reported that Carl Icahn had bought as many as 40 million shares in the company. On Dec. 30, Hertz adopted a poison pill defense, which would allow the company to massively dilute shares to stop a hostile takeover, after seeing unusually high volume and suspicious conditions. Now that it is known that Icahn, and possibly 5% stake holder Dan Loeb, may attempt to change things up at the company, it will be interesting to see how receptive management is to their suggestions.  

One stock that has held its gains fairly well today is Rite Aid (RAD -50.00%) which is up 8.7% this afternoon. The increase comes after the company reported revenue growth of 2.7% in December. Same-store sales for locations open more than one year jumped 4.1%, while revenue from outside the pharmacy rose just 1%, indicating that the sale of drugs is driving growth. This has been a beaten and battered company, but over the past year it has been making a comeback. Investors should be careful, though, as one misstep could send the company back in the dumps.  

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